What is Microscopic Colitis?

Microscopic Colitis is an Inflammatory Bowel Disease that affects the large bowel (colon and rectum). There are two main forms: Lymphocytic Colitis and Collagenous Colitis. These are very similar conditions and commonly referred to under the single name ‘Microscopic Colitis’.

The condition is called ‘Microscopic’ Colitis because, unlike Crohn’s Disease and Ulcerative Colitis, inflammation of the bowel lining is only visible when tissue samples are viewed through a microscope.

In Lymphocytic Colitis, there is an increased number of lymphocytes (white blood cells) within the lining of the colon. In Collagenous Colitis, the lining of the colon develops a thicker than normal layer of collagen – there may also be an increased number of lymphocytes in the lining of the colon.

What are the symptoms?

The main symptom of Microscopic Colitis is chronic, watery diarrhoea.

This may begin very suddenly and occur at any time – it can also lead to dehydration. Unlike Ulcerative Colitis, the diarrhoea does not contain blood, because the lining of the bowel is not ulcerated.

Who gets Microscopic Colitis?

We think that 2-3 people in every 10,000 may develop Microscopic Colitis every year. The condition is most commonly diagnosed in people in their 60's, although the condition may begin at any age.

Both Lymphocytic Colitis and Collagenous Colitis affect more women than men, although the gender differences are greater for Collagenous Colitis.

The number of people with Microscopic Colitis seems to be increasing, but this may be due to growing awareness of the condition and more investigations of older people with chronic diarrhoea.

What causes the condition, and is there a cure?

We don’t know what causes Microscopic Colitis, but that there are likely to be a number of different factors:

Some scientists believe it may be an autoimmune response, where the body’s immune system attacks healthy cells. Reports suggest that up to 4 in 10 people with Microscopic Colitis also have other autoimmune diseases, such as coeliac disease and diabetes.

Some research has suggested that certain drugs may trigger the condition. The drugs most commonly associated with Microscopic Colitis include non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, some proton pump inhibitors, acarbose for diabetes, ranitidine, ticlopidine, and some statins.

Other possible causes include a reaction to bile salts, to bacteria in the gut, or to an infection such as Clostridium Difficile.

Several studies have also shown a link between cigarette smoking and Microscopic Colitis.

What treatments are there for Microscopic Colitis?

Some people find their symptoms stop without treatment. However, many people continue to experience diarrhoea.

There is no cure at present for the condition, but treatment can often relieve these symptoms.

An important first step is to eliminate any other factors that could be contributing to making the diarrhoea worse, including other medical conditions, medications and foods such as dairy products, caffeine or artificial sugars.

If these steps don’t relieve your symptoms, you may need to take medication to manage the condition. This may be anti-diarrhoeal drugs such as loperamide, or budesonide (a steroid drug) amongst others. If these do not work, other drugs may be considered, such as colestyramine or azathioprine. Biologic drugs such as infliximab may also be considered, or another drug called octreocide.

Can Microscopic Colitis develop into Crohn’s Disease or Ulcerative Colitis?

The risk appears to be very small. A few cases have been reported in the past, but the number is very low and it could just be a chance association.

It may also be that Crohn’s or Colitis was mistakenly thought to be Microscopic Colitis when first diagnosed. There can be similarities between the features of each condition and thorough tests are necessary to make the right diagnosis.

Will I recover?

The outlook for people with Microscopic Colitis is generally good. Symptoms tend to improve with time and for many people they resolve completely. Others may continue to have flare-ups but Microscopic Colitis seldom leads to serious complications or surgery.